Equity, Capital and Other Interests EQR Common Shares (Details)	9 Months Ended
	Sep. 30, 2012	Dec. 31, 2011
Common Shares outstanding at January 1,	302,674,716	297,508,185
Common Shares Issued:
Conversion of OP Units	244,785
Issuance of Common Shares	3,173,919
Exercise of share options	1,517,880
Employee Share Purchase Plan (ESPP)	100,222
Restricted Share Grants Net	129,725
Units
Units Issued To Noncontrolling Interests	1,081,797
Common Shares And Units Outstanding	317,074,506
Units Ownership Interest in Operating Partnership	4.50%
Limited Partner [Member]
Units
Total Units Outstanding	14,399,790	13,492,543
Issuance Of LTIPs	70,235
Units Issued To Noncontrolling Interests	1,081,797
Shares Issued During Period Shares Conversion Of Units To Common Shares	(244,785)
Limited Partner [Member]
Units
Total Units Outstanding	14,399,790	13,492,543
Issuance Of LTIPs	70,235
Units Issued To Noncontrolling Interests	1,081,797
Shares Issued During Period Shares Conversion Of Units To Common Shares	(244,785)